docs: def hash_citation(type: str, reference: str) -> str:
      """Create a hash for a type/reference pair of a citation.
  
      :param type: The corresponding citation type
      :param reference: The citation reference
      """
      s = u'{type}:{reference}'.format(type=type, reference=reference)
      return hashlib.sha512(s.encode('utf8')).hexdigest()